Knee joint prosthesis

ABSTRACT

The invention relates to a joint prosthesis for permanent anchorage in the bone tissue of one of the articulatory parts of a joint in a human body, in particular the femur side of a knee joint, primarily intended to be fitted in one operation only. The prosthesis comprises an attachment part (1), intended to be anchored in the human bone tissue by means of a fixture (8), and an articulation element (2) adapted to fit the attachment part (1). The articulation element is attached to the attachment part by a combination of complementary shapes (27, 28, 33, 34) and snap-action locking means (31).

TECHNICAL FIELD OF THE INVENTION

The invention relates to a joint prostesis for permanent anchorage inthe bone tissue of one of the articulatory parts of a joint in a humanbody, in particular the femur side of a knee joint, primarily intendedto be fitted in one operation only, wherein said prosthesis comprises anattachment part, intended to be anchored in the human bone tissue bymeans of a fixture, and an articulation element adapted to fit theattachment part.

BACKGROUND OF THE INVENTION

The present invention is a development of a joint prosthesis of the kinddisclosed in U.S. Pat. No. 5,037,439, to Albrektsson et al. Thisdocument thus inter alia discloses a femoral part of a knee jointprosthesis comprising an articulation element having an inner surface inthe shape of an L. This L-shaped articulation element comprises twoessentially planar parts oriented perpendicularly to each other intendedto be connected to a L-shaped recess cut in the femur bone tissue. Theprosthesis also comprises an elongate intermediate element with a firstside intended to bear against the vertical part of the L-shaped recessin the bone by means of at least one fixture, and a second opposite sideintended to bear against one of the planar parts of the articulationelement. The intermediate element is in the shape of an attachment barhaving flanges provided on said second side intended as a means forholding the articulation element. The back part of the articulationelement is also provided with an elongated means for attachment, havinga T-shaped cross section area, intended to be inserted in saidattachment bar and be locked in a predetermined position by a lockingdevice which consists of locking lugs in the flanges of the intermediateelement.

This prior art discloses a femoral part of a knee joint prosthesis whichcan be fitted in one operation only, which is advantageous since twooperations may entail a greater risk of infection and are troublesomefor the patient.

The present invention is an improvement of the prosthesis describedabove. Due to its shape it has a large area for osseointegrationresulting in a good osseointegration in the bone tissue and thus astable and resistant anchoring in the femur. The parts of the prosthesisall have a relatively simple construction and are easy to fit during oneoperation. The fitting of the articulation element to the attachmentpart is also simple and stable.

Other similar prior art is disclosed for instance in EP 0 183 669.

BRIEF DESCRIPTION OF THE INVENTION

The joint prosthesis of the invention is characterized in that theattachment part comprises a first and a second essentially planar partsoriented generally at an angle relative to each other and joined bymeans of an intermediate part, said attachment part having an innersurface intended to bear on the bone tissue, and an outer surfaceintended to support the articulation element, said outer surface beingprovided with flanges at the two sides oriented mainly in parallel withthe directon of the articulational movment of the joint, said flangesare each being provided with a groove being parallel with one of saidplanar parts which groove is intended to guide and hold correspondingbeads or flanges on said articulation element when said articulationelement is slid onto said attachment part, said attachment part alsobeing provided with a locking device for locking said articulationelement when said element entirely has been slid onto said attachmentpart, said articulation element having a surface being shapedcomplementary to said outer surface of the attachment part, said beadsprojecting from one respective side of said articulation element andhaving a shape complementary to the shape of said grooves in saidflanges.

The joint prosthesis according to the invention preferably is used inthe human knee joint, as a femoral prosthesis, but it can also be usedin other similar joints.

BRIEF DESCRIPTION OF THE APPENDED DRAWINGS

FIG. 1 show one view of an attachment part,

FIG. 2 shows a section along the line A--A in FIG. 3

FIG. 3 shows a section along the line B--B in FIG. 1

FIG. 4 shows the articulation element seen from one side and

FIGS. 5-9 show the different parts of the joint in perspective views.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

In FIGS. 1-4, which illustrate the prosthesis with its two parts indifferent views, 1 designates the attachment part and 2 designates thearticulation element. The attachment part 1 comprises two essentiallyplanar parts, a first part 3 and a second part 4, which are orientedgenerally at an angle relative to each other. These two parts 3,4 arejoined by means of a third intermediate planar part 5, which is somewhatthicker than the two other parts 3,4. The intermediate part 5 is, in itscentral part, provided with a countersunk through hole 6 intended for ascrew 7 for attachment to a fixture 8 (cf. FIGS. 5-9).

The attachment part 1 has inner surfaces 9,9',9" intended to bear on thebone tissue. The inner surfaces 9,9',9" are provided with three guidingand stabilizing flanges 10-12 intended to fit into corresponding grooves13-15 cut in the bone tissue (cf. FIG. 6). The first flange 10 isarranged in the frontal end of the first part 3 and is generallyarranged parallel to the long sides of the first part. The flange 10 hastwo short sides 16,17 oriented at an angle relative to each other. Asecond flange 11 is arranged at the back of the first part 3 and at theintermediate part 5, having a short end 18 being flush with the edge ofthe hole 6. A third flange 12 is arranged in the frontal end of thesecond part 4 and at the intermediate part 5, and it has a short end 19also being flush with the edge of the hole 6 opposite to the end 18mentioned above.

The attachment part has also outer surfaces 20, 20', 20" intended tosupport the articulation element 2. The outer surfaces 20, 20', 20" areprovided with two identical flanges 21,22 arranged on a respective sideof the attachment part 1 which are oriented mainly in parallel with thedirection of the articulational movement of the joint when theattachment part 1 has been fitted. The flanges 21,22 eqch have an outersurface 23,24 with a smooth rounded contour and an inner surface 25,26oriented mainly perpendicularly to the outer surfaces 20, 20', 20" ofthe attachment part 1. Both flanges 21,22 are provided with a straight,elongate groove 27,28 extending along the outer surface 20" of thesecond part 4 over the entire extent of the respective flange 21,22.Each groove thus has one end 29,30 above the intermediate part 5 and andthe other end at the end of the flanges 21,22.

In order to allow the articulation element 2 to be locked to theattachment part 1, the attachment part 1 is provided with a snap-actionlock 31 located at the end of the back part 4. The snap-action lock 31is in the shape of a resilient tongue, which is joined with theremainder of the second part 4 at one end and thus can thus lock thearticulation element 2 by resiliently engaging a recess 51 on the innersurfaces 32,32',32" of the articulation element 2.

The articulation element 2 can most easily be seen in FIG. 4, in whichthe element is illustrated in a side view. The element 2 has innersurfaces 32,32',32" intended to bear on the attachment part 1, saidsurfaces having a shape complementary to the outer surfaces 20, 20', 20"of the attachment part 1. The articulation element 2 is provided withtwo beads 33,34, each projecting from one respective side of thearticulation element 2. They are intended to fit into the grooves 27,28and have a shape complementary to the shape of the grooves 27,28. Theouter surface 35 of the articulation element 2 is adapted to fit ameniscus to be used in combination with the prosthesis.

In FIG. 5-7 and 9 are the different parts of the joint illustratedduring different phases of the operation. The first step is toaccurately prepare the bone end for the implant by cutting the femoralbone tissue to have planar surfaces 36, 36',36" having a shapecorresponding to the shape of the inner surfaces 9, 9', 9" of theattachment part 1. Then a hole 37 is drilled in the central surface ofthe recess 36'. A fixture 8, in the shape of a screw having an innerbore part 39 provided with internal threads is screwed into the hole 37.The fixture 8 is provided with transverse grooves 40-43 at its outerend. The fixture 8 is inserted in such a way that two of the grooves, inthis case the grooves 40,41, are oriented mainly in parallel with thedirection of the articulational movement of the joint, i.e. along thelongitudinal direction of the attachment part 1. The next step is to cutthe grooves 13-15. The two grooves 14,15 are cut as extensions of thetwo transverse grooves 40,41 in the fixture 8. The groove 13 is cut inthe frontal end of the surface 36 in the bone tissue. The attachmentpart 1 is then placed on the surfaces 36, 36', 36", being guided to thecorrect position by the stabilizing flanges 10-12, which fit into thecorresponding grooves 13-15, the flanges 11,12 at the same time fittinginto the transverse grooves 40,41. In this way, the fixture is lockedagainst rotation.

The attachment part 1 then is attached to the cut bone surface by meansof an attachment screw 7 which is screwed into the fixture 8.

The final step is to connect the articulation element 2 to theattachment part 1. This is performed by fitting the beads 33,34 intocorresponding elongate grooves 27,28 and sliding the articulationelement 2 along the grooves 27,28 until the element abuts the outersurfaces 20,20',20' of the attachment part 1. When the articulationelement 2 entirely has been slid on to the attachment part 1, it islocked by the snap-action lock 31. The operation is then completed.

In FIGS. 6--7 a second embodiment of the attachment part 1 is shownwhere a locking device corresponding to the snap-action lock 31 isarranged on each side of the flanges 21,22. This locking device isformed by those parts of the flanges 21,22 which are located between theperpendicular transverse slits 45-48 cut in each of the flanges 21,22.Grooves 49,50, extending in parallel to the outer surface 20 of theattachment part 1, are provided on the inner surfaces of the parts ofthe flanges 21,22 located between the transverse slits 45-48. By thesemeans a kind of snap-action lock is formed functioning as a resilienttongue which can engage the articulation element 2 resiliently. Whenthis embodiment is used, the articulation element will be provided withadditional beads fitting into the horisontal grooves 49,50.

FIG. 8 shows a further embodiment of the invention wherein the outersurface 20, on that planar part 3 which is not parallel with the grooves27,28, is provided with a conical plug 52 adapted to to fit into acomplementary conical recess or cavity 53 provided in the inner surface32 of the articulation element 2. This conical plug 52 will, inconjunction with the conical recess 53, further stabilize thearticulation element 2 relative to the attachment part 1. This featuremay be of particular interest when the flanges 21,22 are to function asresilient locking tongues.

The invention can of course be varied in many ways within the scope ofthe claims.

We claim:
 1. A joint prosthesis requiring only one operation to bepermanently anchored in the bone tissue of one of the articulating partsof a joint in a human body, in particular the femur side of a kneejoint, said prosthesis comprising:a) an attachment having an innersurface for bearing against the bone tissue and an outer surface, theattachment including: a first and a second essentially planar partoriented generally at an angle relative to each other; an intermediatepart joining the planar parts; and flanges disposed on the outer surfaceover the planar parts and the intermediate part and oriented parallel tothe direction of articulation movement of the joint, the flanges eachhaving a groove disposed over and oriented parallel to the second planarpart; b) means for securing the attachment to the bone tissue; c) anarticulation element disposed over the outer surface of the attachmentand having an interior shape which is complementary to the outersurface, the articulation element including beads projecting fromopposed side surfaces of the articulation element and engaging thegrooves; and d) locking means for fixing the articulation element to theattachment when the articulation element is disposed over the attachmentand the beads are engaged in the grooves.
 2. A joint prosthesisaccording to claim 1, further comprising a plurality of stabilizingflanges disposed on the inner surface of the attachment for fitting intocomplementary grooved areas cut in the bone tissue for guiding andstabilizing the attachment in the bone tissue.
 3. A joint prosthesisaccording to claim 2, wherein the intermediate part has a countersunkthrough-hole located above a hole cut in the bone and the means forsecuring the attachment to the bone tissue comprises:an externallythreaded fixture for screwing into the hole cut in the bone tissue, thefixture including an inner bore provided with internal threads and anouter end disposed at the surface of the bone tissue when the fixture isscrewed into the hole, the outer end having at least one transversegroove in line with one of the grooved areas cut in the bone tissue; andan attachment screw for being screwed into the inner bore of the fixtureand having a head which sits in the countersunk through-hole forsecuring the attachment to the bone tissue; wherein one of thestabilizing flanges on the inner surface of the attachment is fittedinto at least one transverse groove to prevent the fixture fromrotating.
 4. A joint prosthesis according to claim 1, wherein thelocking means is in the shape of a snap-action lock arranged in thesecond planar part being parallel with said grooves and comprises aresilient tongue extending from the second planar part and engaged to arecess on the interior of the articulation element.
 5. A jointprosthesis according to claim 1, further comprising a conical plugdisposed on the outer surface of the attachment for fitting into acomplementary conical recess located on the interior surface of saidarticulation element.